In recent years, many electronic devices transmitting electric power in a non-contact manner have been developed. So as to transmit electric power in a non-contact manner in electronic devices, in many cases a power transmission system based on a magnetic field coupling method is adopted where coil modules are provided in both of a power transmitting unit for electric power and a power receiving unit for electric power.
However, in the magnetic field coupling method, the intensity of a magnetic flux passing through each coil module is greatly influenced by an electromotive force, and so as to transmit electric power with high efficiency, high accuracy is required for positioning of relative positions in a coil planar direction of a coil module on a power transmitting unit side (primary side) and a coil module on a power receiving unit side (secondary side). In addition, since the coil modules are used as coupling electrodes, the miniaturization of the power transmitting unit and the power receiving unit is difficult. Furthermore, in an electronic device or the like, it is necessary to consider an influence on a storage battery due to the heat generation of a coil, and there has occurred a problem that it becomes a bottleneck on layout design.
Therefore, for example, a system for transmitting electric power using an electrostatic field is disclosed. In Patent Document 1, an energy carrying device is disclosed where a high power transmission efficiency is realized by forming a strong electric field between a coupling electrode on a power transmitting unit side and a coupling electrode on a power receiving unit side. In Patent Document 1, a passive electrode having a relatively large size and an active electrode having a small size are provided on the power transmitting unit side, and a passive electrode having a relatively large size and an active electrode having a small size are also provided on the power receiving unit side. By forming the strong electric field between the active electrode on the power transmitting unit side and the active electrode on the power receiving unit side, the high power transmission efficiency is realized. So as to form the strong electric field, there are taken a measure such as shortening a distance between electrodes on the power transmitting unit side and the power receiving unit side or increasing a facing area between electrodes facing each other.
Patent Document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-531009
Recently, in even an electronic device not having a non-contact power transmission function, so as to be able to transmit electric power without being physically connected, a power receiving jacket capable of transmitting electric power from an external power transmitting unit in a non-contact manner is attached to the electronic device, and it is possible to transmit electric power through the power receiving jacket to the electronic device, by forming a strong electric field between a coupling electrode of the power receiving jacket and a coupling electrode on the power transmitting unit side. FIG. 1 is a schematic view illustrating the configuration of a non-contact power transmission system at the time of attachment of a power receiving jacket of the related art.
In FIG. 1, in a power transmitting stand (power transmitting unit) 1 including a power transmitting module 10, a passive electrode 11p is provided in a surface to which a power receiving jacket 2 is attached and which supports the power receiving jacket 2, and an active electrode 11a is provided in a surface to which the power receiving jacket 2 is attached. A power receiving unit 4 includes the power receiving jacket 2 to which an electronic device 3 is attached, and the power receiving jacket 2 includes a power receiving circuit module 27 and a DC-DC converter 24. In the power receiving jacket 2, an active electrode 21a is disposed at a position facing the active electrode 11a provided in the surface of the power transmitting stand 1 to which the power receiving jacket 2 is attached, and an passive electrode 21p is disposed at a position facing the passive electrode 11p provided in the surface of the power transmitting stand 1 to which the power receiving jacket 2 is attached and which supports the power receiving jacket 2. As is understood from FIG. 1, while it is possible for the active electrode 11a in the power transmitting stand 1 and the active electrode 21a in the power receiving jacket 2 to secure a sufficient facing area, it is difficult for the passive electrode 11p in the power transmitting stand 1 and the passive electrode 21p in the power receiving jacket 2 to secure a sufficient facing area. Accordingly, there has been a problem that it is difficult to enhance the transmission efficiency of electric power.
On the other hand, FIG. 2 is a schematic view illustrating another configuration of the non-contact power transmission system at the time of attachment of the power receiving jacket 2 of the related art. FIG. 2 is different from FIG. 1 in that the passive electrode 21p in the power receiving jacket 2 is stretched to a position where it is possible for the passive electrode 21p to face the surface of the power transmitting stand 1, which supports the power receiving jacket 2. In doing this way, it is also possible to secure a sufficient facing area with respect to the passive electrode 11p in the power transmitting stand 1 and the passive electrode 21p in the power receiving jacket 2 and it is possible to enhance the transmission efficiency of electric power. However, since it is necessary to increase the size of the passive electrode 21p in the power receiving jacket 2, there has been a problem that a manufacturing cost increases.